netdev - [PATCH net] genetlink: fix genl_bind() invoking bind() after -EPERM

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Message-ID: <20250831190315.1280502-1-alok.a.tiwari@oracle.com>
Date: Sun, 31 Aug 2025 12:03:13 -0700
From: Alok Tiwari <alok.a.tiwari@...cle.com>
To: jiri@...dia.com, stanislaw.gruszka@...ux.intel.com, andrew+netdev@...n.ch,
        davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
        pabeni@...hat.com, horms@...nel.org, netdev@...r.kernel.org
Cc: alok.a.tiwari@...cle.com
Subject: [PATCH net] genetlink: fix genl_bind() invoking bind() after -EPERM

Per family bind/unbind callbacks were introduced to allow families
to track multicast group consumer presence, e.g. to start or stop
producing events depending on listeners.

However, in genl_bind() the bind() callback was invoked even if
capability checks failed and ret was set to -EPERM. This means that
callbacks could run on behalf of unauthorized callers while the
syscall still returned failure to user space.

Fix this by only invoking bind() if (!ret && family->bind)
i.e. after permission checks have succeeded.

Fixes: 3de21a8990d3 ("genetlink: Add per family bind/unbind callbacks")
Signed-off-by: Alok Tiwari <alok.a.tiwari@...cle.com>
---
 net/netlink/genetlink.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/netlink/genetlink.c b/net/netlink/genetlink.c
index 104732d34543..3b51fbd068ac 100644
--- a/net/netlink/genetlink.c
+++ b/net/netlink/genetlink.c
@@ -1836,7 +1836,7 @@ static int genl_bind(struct net *net, int group)
 		    !ns_capable(net->user_ns, CAP_SYS_ADMIN))
 			ret = -EPERM;

-		if (family->bind)
+		if (!ret && family->bind)
 			family->bind(i);

 		break;
-- 
2.50.1